Noise controlling housing

ABSTRACT

A noise controlling housing for lawn or garden tractors providing a sound barrier between the noise source within the housing and the space outside the housing. The housing is formed from a plurality of tightly fitted compound curved walls. The walls define noise barriers which because of their tight fit minimize pressure pulsations of incident sound waves from being transmitted through unnecessary openings in the housing, and because of the compound curved walls prevent the pressure pulsations from the noise source from vibrating or flexing the walls thereby generating sound waves outside the housing.

D United States Patent 1111 3,884,322

Nemschoff 1 May 20, 1975 [541 NOISE CONTROLLING HOUSING FOREIGN PATENTS OR APPLICATIONS 1 1 Inventorr Mark Nemschoif, q t 746,702 3/1956 United Kingdom 181/33 K 1 1,089,646 9/1960 Germany 4. 180/69 R [73 Asslgnee' FMC Corpommn San Jose 700,730 12/1953 United Kingdom..... 296/28 R [22] Filed: Apr. 27, 1973 1,034,323 7/1953 France ISO/l F 480,562 8/1927 Germany 180/69 R [21] Appl. No.: 355,105

Primary Examiner-Stephen J. Tomsky 52 us. 01 181/33 K; 56/1714; 180/69 R Assistant Examiner-Wt Miska 51 Int. Cl. GlOk 11/00 y. Agent, or Moore: 0 PP [58] Field of Search 123/198; 56/229, 233238;

180/69, 54 D; 181/33 K; 296/28 ABSTRACT A noise controlling housing for lawn or garden trac- [56] References Cited tors providing a sound barrier between the noise UNITED STATES PATENTS source within the housing and the space outside the housing. The housing is formed from a plurality of 0 03 1191] C1 k 180 69C i 2 611936 j z 180469 R tightly fitted compound curved walls. The walls define 2'71 1:341 6/1955 Mills et a]. 180/69 R noise barriers which because of their tight fit minimize 2726,502 12 1955 Hall 56 152 pressure pulsations of incident sound waves from 2,962,107 1l/l960 Mihal et al.... I. 180/69 R being transmitted through unnecessary openings in the 1180, /1 e es v l/69 R X housing, and because of the compound curved walls T3011 1 prevent the pressure pulsations from the noise ource g if from vibrating or flexing the walls thereby generating 3613338 10/1971 P3161111? :1: 56/175 Sound outside the housing 3,796,277 3/1974 Gordon /69 R 4 Claims, 6 Drawing Figures PATENTED HAY 2 01975 SHEET 10F 5 PMENTEWQ $884,322

SHEET 5 BF 5 FII3 EI NOISE CONTROLLING HOUSING BACKGROUND OF THE INVENTION 1. Field of the Invention This invention pertains to noise controlling mechanisms for garden and lawn type tractors, and more particularly relates to a housing defined by compound curved sheet metal walls, which compound curved walls resist vibration and thus minimizes transmission of noise outside the housing.

2. Description of Prior Art Small tractors such as lawn or garden tractors are inherently rather noisy because of the type of engines used. Although the noise level has been reduced somewhat by large mufflers, by reducing the engine speed, and by controlling rattles; heretofore there has been little effort or incentive to further reduce the noise level of such tractors. With increased emphasis placed on noise control by governmental agencies, and with new noise level standards going into effect, it has become apparent that additional noise reducing barriers are necessary.

Most prior art tractors have their engines disposed only within a hood and grille with the remaining portion of the engine directly exposed thus providing no sound barrier for horizontal sound waves moving transversely away from the engine. It has been determined that flat sheet metal walls when positioned to intersect these waves tend to resonate and act as drums which broadcast noise generated within the housing outside the housing.

SUMMARY OF THE INVENTION The noise controlling housing of the present invention encloses the tractor engine and muffler and includes a plurality of non-resonating curved sheet metal panels or walls which serve as sound deadening barriers thus minimizing the broadcast of noise. These walls are preferably compound curved walls since the curvature in two directions strengthens the walls and greatly reduces the tendencies of the walls to resonate. The walls are tight fitting to prevent direct sound leakage through unnecessary cracks, holes and other openings and to prevent rattle thus further reducing the noise level to a level of about 69 dba for a tractor having a 7 16 horse power engine. The compound curved walls have the added advantage of enhancing the appearance of the tractor.

It is, therefore, one object of the present invention to provide a noise controlling housing for a garden tractor or the like.

Another object is to provide a noise controlling housing having a plurality of non-resonating compound curved sheet metal walls.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective of a garden tractor incorporating the noise controlling housing of the present invention.

FIG. 2 is a longitudinal vertical central section of the housing with the housing being illustrated in full lines in its normal operating position, and with the hood and grille of the housing shown in phantom lines in an open engine servicing position.

FIG. 3 is a horizontal section taken along lines 33 of FIG. 2 illustrating the curvature of the grille and side walls panels relative to a generally vertical axis.

LII

FIG. 4 is a top plan of the housing illustrating the curvature of the side walls of the hood relative to vertical axes.

FIG. 5 is a vertical transverse section taken along lines 5-5 of FIG. 2 illustrating the curvature of the side walls and hood relative to longitudinally extending generally horizontal axes.

FIG. 6 is a transverse section through a portion of the tractor frame taken along lines 6--6 of FIG. 2 and showing their rear end closures or wings of the hood.

DESCRIPTION OF THE PREFERRED EMBODIMENT The noise controlling housing 10 (FIGS. 1 and 2) of the present invention is shown mounted on a garden tractor 12, and in general includes a front portion provided with grille 14, a top portion including hood 16, and two side panels 18 and 20 (FIG. 5).

The tractor 12 includes a chassis 24 supported on two drive wheels 26 (only one being shown in FIG. 1) and two steerable wheels 28. The chassis carries an air cooled engine 30 (FIGS. 2 and 5) having an air cleaner 32 and a muffler 34 with a forwardly directed exhaust pipe 36. Cooling air is drawn into the housing from beneath the tractor and is discharged through perforations in a compound curved wall 38 defining the perforated grille 14 after cooling the engine and muffler. Vents 40 are provided in the hood 16 to assist in the discharging of the air.

The grille 14 and hood 16 are joined together and are pivoted as a unit between the solid and the dotted line positions of FIG. 2 thereby providing easy access to the engine 30. The grille 14 is pivotally connected to the chassis by spaced brackets 44 (FIGS. 2 and 3) fitted into slots 46 in the bottom flange 48 of the grille. The bottom flange 48 is reinforced by angle members 50. The angle members 50, slots 46, and brackets 44 are arranged so that separation of the hood and grille from the chassis is precluded when these components are in their solid line positions (FIG. 2), but the hood and grille may be separated from the chassis after being pivoted to the phantom line position by merely pulling the slots 46 free from the brackets 44. When in its operative, noise deadening position, the rear edge of the hood is held firmly against an inverted U-shaped frame member 52 that is rigidly secured to the chassis. A rubber cushioning strip 53 is secured to the rear edge of the hood to provide a tight rattle proof connection between the hood and the frame member 52. The frame member 52 includes a rear closure or wall 54 defined by an instrument panel.

More particularly, the grille 14 (FIGS. 2-4) comprises a sheet metal structure with stamped opening 60 for headlight 62 (FIG. 1) and a pair of vent openings 64 partially defined by a central vertical rib 68 with which the perforated wall 38 is rigidly secured. It will be noted that the edges of all openings 60, 64 are pressed inwardly to form flanges 60a, 64a which are about 1 4 inches wide. Also, the outer peripheral edges of the grille are pressed inwardly to provide a peripheral skirt 70 which includes the bottom flange 48.

As illustrated in FIGS. 3 and 4, the forward faces of the grille 14, and the perforated wall 38, are horizontally curved about a generally vertical axis (not shown) passing through the longitudinal axis of the tractor with the radius of curvature being within the range of about to inches, preferably 1 l0 inches. As illustrated in FIG. 2, the grille and perforated walls 38 are vertically curved about a generally horizontal axis and have radius of curvatures within the range of about 60 to 200 inches, preferably 84 inches. Also as evident from FIG. 5, the upper portion of the skirt 70 has a curvature generated about a longitudinally extending, generally horizontal axis having a radius of curvature within 'the range of 30 to 80 inches, preferably 42 inches; while the side portions of the skirt 70 have curvatures generated about longitudinally extending, generally horizontal axes having radii of 'curvatureswithin the range of 30 to 80 inches, preferably 60 inches. Thus, the forward face of the grille 14 and the perforated air cooling walls 38 of the grille define compound curved nonresonating sheet metal walls which resist drumlike broadcasting of noise.

The hood 16 is pressed from sheet metal and as indicated in FIGS. 1, 2 and has its upper wall 78 provided with louvers 80, which define the vents 40. The wall 78 and louvers are curved about a generally horizontal, longitudinal extending axis that is within the range of curvature of 30 to 80 inches, preferably 42 inches. Relatively short, downwardly extending side walls 82 are preferably linear but outwardly diverging in transverse section as illustrated in FIG. 5. The lower edges of the side walls 82 are bent over to provide double thickness edges 83 for tighter seated engagement with the side panels 18 and 20.

Because of the louvers 80 (FIG. 2) formed in the forward segment 78a of the upper wall 78 of the hood 16, and because of an upwardly inclined rear segment 78b which nests over and is rigidly secured to the upstanding U-shaped frame member 52 during operation, it has been determined that the upper wall 78 as viewed in 'FIG. 2 need not be curved but may be formed in longitudinally extending linear segments 78a and 78b separated by a bend line at 84. However, it is within the scope'of this invention to provide a curvature of segment 78a .in the plane of FIG. 2 that has a radius within the range of O to 100 inches.

Having reference to FIG. 4, it will be noted that the side walls 82 and longitudinal edges of the upper wall 78 of the hood 16 are curved about vertical axes having radii of curvatures lying within the range of about 100 to 180 inches, preferably about 165 inches. As viewed in FIGS. 4 and 6, the hood also includes narrow wings 86 sloped rearwardly, downwardly, and inwardly which wings seat against the frame member 52.

'- 1 The side panels 18 and 20 are quite similar to'each other and as illustrated in FIGS. .2 and 5 each panel includes a lower mounting flange 88 which is slotted to receive cap screws which are screwed into a threaded portion of the chassis. Also, each panel includes a vertically extending wing 90 provided with a slot 92 to re- I ceive a cap screw (not shown) which is screwed into a threaded hole in an upstanding portion of the tractor frame to rigidly support the .rear end of the panels. The upper edge of each panel 18 and 20 is defined by an inwardly bent flange 94 which tightly receives the double ative position. Also, the lower rear corner of the right hand panel 18 is relieved at 100 (FIG. 3) to permit operation of a foot pedal (not shown) which is used to operate a hydrostatic transmission used in the tractor. Apertured indentations 102 are formed in each panel 18 and 19 to receive side reflectors 104 for night operation.

As illustrated in FIG. 3, the panels 18 and are each vature within the range of to 80 inches, preferably 60 inches.

It will be appreciated that when the noise controlling housing 10 of the present invention is bolted in its closed operative positions illustrated in FIGS. 1 and 2, that the engine 30 and muffler 34 which combine to define'a noisesource, are completely shielded by the thickness lower edge 83 of the associated side walls 82 of the hood. Also, the forward edges of the panels are provided with inwardly bent flanges 98 (FIG. 3) for firm sealing against the skirt of the grille 14 when the hood is closed. As illustrated in FIG. 5, an upper portion of the wing of panel 18 is relieved at 99 to receive a component of the tractor (not shown) which closes this relieved portion when the hood is in its operhousing 10 except for the openings necessary for allowing cooling air to enter the housing and cool the engine and muffler. Tests have been conducted with the results indicating that the 16 horse power tractor operates at 69 dba which is quieter than proposed standards which are to go into effect in 1975 in at least one large city in the United States.

From the foregoing description it is apparent that the noise controlling housing of the present invention includes a plurality of tight fitting housing walls which minimize the uninterrupted transmittal of sound waves from the noise producing source to the outer atmosphere by direct sound leakage. Also, the plurality of tightly fitting walls include compound curved walls which prevent the walls from resonating in response to sound waves generated by the enclosed engine. Thus, the non-resonating compound curved, sheet metal panels serve to greatly minimize sound from the tractor engine to be transmitted outside the noise controlling housing of the present invention.

Although the best mode contemplated for carrying out the present invention has been herein shown and described, it will be apparent that modification and variation may be made without departing from what is regarded to be the subject matter of the invention.

What I claim is:

1. In a garden tractor or the like having an engine and a muffler together defining a noise source supported on a wheeled chassis and having grille and curved hood means on said tractor adjacent said engine, the improvement comprising:

a noise-controlling housing including front, side, and top portions fully enclosing said engine and said muffler on the front, top and sides,

said housing front portion including said grille,

said housing top portion including said curved hood,

said housing side portions constituting side panels extending rearwardly from said grille and beneath the side edges of said hood,

the major area of said housing front portion defining a compound curved surface bowed about two axes lying in different planes substantially normal to each other,

the major area of said housing side panels each defining like opposed compound curved surfaces each bowed about two axes lying in different planes substantiall'y normal to each other, said compound curved surfaces of said housing front, side and top portions thereby together defining substantially non-resonating curved sheet metal walls whereby said housing is effective to reduce externally thereof the sound emitted from said sound source to a level substantially below that of a tractor having a comparable noise source but without said enclosing housing having said compound curved'surfaces. 2. A noise controlling housing according toclaim 1 wherein said grille includes at least one opening covered by a perforated compound curved wall; wherein saidperforated wall has a radius of curvature of between 60 and 200 inches about an axis lying in a generally horizontal plane, and has a radius of curvature of between about 100 and 180 inches lying in a generally vertical plane; whereinsaid grille includes a compound curved forward stiffening wall having a radius of curvature about the same axes as said perforated wall, and wherein the radii of curvatures are about one inch greater than that of said perforated compound curved 6 wall.

3. A noise controlling housing according to claim 1 wherein the radius of curvature of each side panel is about one axis lying in a generally horizontal plane and lies within a range of about 30 to inches, and wherein the radius of curvature is about another axis lying in a generally vertical plane and is within the range of about to inches.

4. A noise controlling housing according to claim 3 wherein the grille includes at least one opening covered by a perforated, compound curved wall; wherein said perforated wall has a radius of curvature of between 60 and 200 inches generated about an axis lying in a generally horizontal plane, and has a radius of curvature of between about 100 and l80 inches generated about an axis lying in a generally vertical plane wherein said hood includes an upper wall having air vents defined by louvres formed therein and has a radius of curvature generated about a generally horizontal longitudinally extending axis lying within the range of about 30-80 inches.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT N0..: 3,884,322 DATED May 20, 1975 INVENTORG) 2 MARK S. NEMSCHOFF It is certified that error appears in the above-identified patent add that said Letters Patent are hereby corrected as shawn below;

7:. Column '2, llne 19: after "s1de" Insert portlons providing side Signd ahd Scaled this rwenrierh D y of January 19 6 [SEAL] Arrest:

RUTH C. MASON Arresting Officer C. MARSHALL DANN Commissioner of Patents and Trademarks UNITED STATES PATENT OFFIQE CERTIFICATE OF CORRECTION PATENT N0. 3,884 ,322

DATED May 20, 1975 INVENTORB) 1 MARK S. NEMSCHOFF It iscertified that error appears in the above-identified pate rrt arrdthat said Letters Patent are hereby corrected as shown below:

Column '2, 'line 19: after s1de" lnsert portlons providing side Signd ahd Scaled this twentieth D y of January 1976 [SEAL] A ttest:

C. MARSHALL DANN Commissioner uflatents and Trademarks RUTH C. MASON Arresting Officer 

1. In a garden tractor or the like having an engine and a muffler together defining a noise source supported on a wheeled chassis and having grille and curved hood means on said tractor adjacent said engine, the improvement comprising: a noise-controlling housing including front, side, and top portions fully enclosing said engine and said muffler on the front, top and sides, said housing front portion including said grille, said housing top portion including said curved hood, said housing side portions constituting side panels extending rearwardly from said grille and beneath the side edges of said hood, the major area of said housing front portion defining a compound curved surface bowed about two axes lying in different planes substantially normal to each other, the major area of said housing side panels each defining like opposed compound curved surfaces each bowed about two axes lying in different planes substantially normal to each other, said compound curved surfaces of said housing front, side and top portions thereby together defining substantially nonresonating curved sheet metal walls whereby said housing is effective to reduce externally thereof the sound emitted from said sound source to a level substantially below that of a tractor having a comparable noise source but without said enclosing housing having said compound curved surfaces.
 2. A noise controlling housing according to claim 1 wherein said grille includes at least one opening covered by a perforated compound curved wall; wherein said perforated wall has a radius of curvature of between 60 and 200 inches about an axis lying in a generally horizontal plane, and has a radius of curvature of between about 100 and 180 inches lying in a genErally vertical plane; wherein said grille includes a compound curved forward stiffening wall having a radius of curvature about the same axes as said perforated wall, and wherein the radii of curvatures are about one inch greater than that of said perforated compound curved wall.
 3. A noise controlling housing according to claim 1 wherein the radius of curvature of each side panel is about one axis lying in a generally horizontal plane and lies within a range of about 30 to 80 inches, and wherein the radius of curvature is about another axis lying in a generally vertical plane and is within the range of about 100 to 180 inches.
 4. A noise controlling housing according to claim 3 wherein the grille includes at least one opening covered by a perforated, compound curved wall; wherein said perforated wall has a radius of curvature of between 60 and 200 inches generated about an axis lying in a generally horizontal plane, and has a radius of curvature of between about 100 and 180 inches generated about an axis lying in a generally vertical plane wherein said hood includes an upper wall having air vents defined by louvres formed therein and has a radius of curvature generated about a generally horizontal longitudinally extending axis lying within the range of about 30-80 inches. 